keyboard: Don't report activity on key release

With phosh 0.25, using the power button to blank the screen became rather annoying, as holding it for a bit longer (about a quarter of second) causes the screen to come back on right after releasing the button. This happens because idle timers set up by phosh on screen blank are being fired on power button release.

Until phosh can subscribe and properly react to button releases too, resolve it by not reporting activity on button release.

Signed-off-by: Sebastian Krzyszkowiak sebastian.krzyszkowiak@puri.sm